Remove and improvement a unnecessary method(getMountPath()).
- getMountPath() of TajoMaster is not use. So it be remove.
- getMountPath() of TajoWorker is only use in initCleanupService() of TajoWorker. It is in order that get count of worker temporal dir. But getMountPath() is unobtainable correct count. It can get in WORKER_TEMPORAL_DIR of config.